Field of the Invention
Aspects of the present invention relate to a liquid-discharging-head substrate for use a liquid discharging head configured to discharge liquid, a liquid discharging head including the liquid-discharging-head substrate, a liquid discharging apparatus including the liquid discharging head, and a method of manufacturing the liquid-discharging-head substrate.
Description of the Related Art
A liquid-discharging-head substrate for use in a liquid discharging head includes heating resistor elements for discharging liquid. In recent years, there has been a demand for densely arranging the heating resistor elements in order to downsize the substrate. Further, there also has been a demand for a liquid discharging head with high durability and low power consumption.
Japanese Patent Application Laid-Open No. 11-10882 discusses a liquid-discharging-head substrate in which a first electrode wiring layer, an intermediate insulation layer, and a heating resistor element layer are provided in this order. The heating resistor element layer is electrically connected to the first electrode wiring layer via a through-hole section formed in the intermediate insulation layer. Further, the heating resistor element layer is electrically connected to a second electrode wiring layer formed beneath the heating resistor element layer. In this way, the first and second electrode wiring layers are arranged in a three-dimensional folded structure in stacking direction beneath the heating resistor element layer in the substrate. This makes it possible to narrow intervals between adjacent heating resistor elements and thus densely arrange the heating resistor elements.
Further, in the structure discussed in Japanese Patent Application Laid-Open No. 11-10882, a surface including the intermediate insulation layer, the through-hole section, and the second electrode wiring layer is flattened using a chemical-mechanical polishing (CMP) method, and the heating resistor element layer is formed on the flattened surface. Meanwhile, in a case of a structure in which a thick layer such as an electrode wiring layer is formed on a heating resistor element layer, which is a different structure from the above structure, if a coating layer with which the electrode wiring layer is coated is thinly formed, a pinhole or crack may be formed in a large step height of the coating layer created by the electrode wiring layer. On the other hand, in the structure discussed in Japanese Patent Application. Laid-Open No. 11-10882, no step height is created by the electrode wiring layer, and the layer coating the heating resistor element layer is formed on the flattened surface, so even when the coating layer is thinly formed, the heating resistor element layer is coated properly. Thus, thermal energy can be applied efficiently to liquid to reduce the power consumption of the liquid discharging head.